Procedures, in which two slabs made of different materials are combined to one composite material by a hot-rolling process in order to be able to deliberately adjust or realize properties of the composite material, are sufficiently known from the prior art. Typically, the composite partners with the same size are arranged one above the other and welded together peripherally in order to prevent the formation of cinder and to transport the joined composite partners as safely as possible to the hot-rolling device. Since the slabs generally have unevenness, air chambers can form during the welding process, which can also still be found as bubbles between the composite partners after the hot-rolling process.
In order to counteract this formation of bubbles, procedures are known from the prior art, for example from publication EP 0 004 063, in which the elaborate attempt is made to evacuate air from between the work piecework pieces, before the composite partners are rolled to produce a composite material.